1. Field of the Invention
The present invention relates to prostheses and, more particularly, to an anti-slip anchoring system with drainage feature that securely anchors a suction liner with a top-side and lower lanyard-type attachment to prevent extraneous motion for above-the-knee and below-the-knee amputation patients, and which drains moisture from sweat to improve comfort without sacrificing stability.
2. Description of the Background
There are a variety of different types of prosthetic devices for patients that have had either transfemoral (above-knee) or transtibial (below the knee) amputation. Typically, post-operative prosthetic devices for either type of amputation patients begin with a liner, which is rolled on to the residual limb. The liner is a soft, stretchy material that acts as an interface with the prosthesis.
Once the liner is on, the residual limb then slides into a hard socket. This socket is specially made to fit and can be made out of a variety of materials.
The hard socket for a transfemoral prosthesis has a knee joint connected to it, and the more natural the movement of the knee the better. Transtibial prostheses have no knee joint. In both cases (with or without a knee joint) there typically is an aluminum or carbon fiber tube to which a foot module is connected. There are a number of difficult goals for the design of transfemoral and/or transtibial prostheses (above & below the knee). For one, it is very important that the socket be securely fitted to the limb and secured in place. Stability is a common problem as many existing anchoring systems use a single attachment point to hold the residual limb in place, and this typically leads to extraneous pivoting, rotation and shift during ambulation. Moreover, it is important to be able to adjust the anchoring system periodically because the mass of the limb may change significantly over the course of a day. The limb tends to change size (swell or contract) depending on use, temperature, etc. Still another goal is to minimize or evacuate moisture from within the liner. The liner is a rubber sheath and promotes heavy sweating, especially when the patient takes part in physical activities (running, etc.) that induce sweating. With most prosthetic devices the patient needs to remove the prosthesis periodically and simply pour the sweat out. This is not a convenient solution.
U.S. Pat. No. 5,653,766 to Naser issued Aug. 5, 1997 shows a prosthetic device 20 having a generally cylindrical socket 24 with an opening for receiving an amputated limb. The socket 24 is closed at the other end, and is mounted on a bendable knee joint. Once the limb is properly received within the socket 24, straps 38 are adjusted so that a secure fit is achieved. This essentially uses a radial pressure-fit imposed by tightening the two belts. However, this tends to squeeze the limb unevenly and adds to discomfort. Moreover, the radial pressure tends to pop the limb out of the socket over the course of a day.
Another well-known ICEX® Socket System uses a combination lanyard and pin kit as a docking and locking mechanism. The socket has a distal pin that docks with the prosthesis. A lanyard is connected to the liner through a slot in the bottom of the socket. The lanyard is pulled to allow the patient's residual limb, which is enclosed in the silicone liner, to be drawn into the socket by the lanyard. The lanyard is then anchored to the front of the socket. The lanyard has the advantage of allowing for adjustment of position within the ICEX Socket. If the limb changes position because of volume change and the distal migration of the limb into the socket, the prosthesis can easily be adjusted by the lanyard to compensate. The lanyard method of donning the socket also significantly reduces pain directly related to the donning process with a pin-locking mechanism. However, it has been found that many amputees lack the room for, are unable to tolerate, or have difficulty engaging the distal pin. Others complain of pain associated with engagement of the pin.
There are a number of Asuspension″ type sockets that eliminate the pin. U.S. Pat. No. 6,645,253 to Caspers issued Nov. 11, 2003 shows a suction system that employs a vacuum pump to impart suction to the liner, the vacuum pump doubling as a shock absorber for the artificial limb. Commercially, this is known as the Harmony® System. FIG. 1 is a perspective view of the Harmony System, which pulls air from the sealed socket 12 and also evacuates moisture (sweat) buildup. A nonporous polyurethane liner (not shown) is fitted over the residual limb and is inserted in the socket 12. A vacuum pump 30 is attached via a connector block 20 beneath the socket 12 to create a vacuum force which is coupled by a tube to the socket, thereby evacuating air and sealing it to the residual limb. This provides a total-contact hypobaric suction equal weight distribution socket liner which tacks up to the skin of the residual limb and provides total contact with the limb. Research has shown that patients lose six to twelve percent of their residual limb volume in the course of a day, leaving the limb smaller than the prosthetic socket. With the Harmony System vacuum-assisted technology, the residual limb size stays the same and the prosthesis fits better all day long. The existing Harmony System as described in the '253 patent is a suspension system which uses a liner with no mechanical connection between the liner and socket, but also suggests a mechanical interlock such as a distal pin on the liner (similar to that of the ICEX Socket System) that fits into the socket. Again, many amputees lack the room for, are unable to tolerate, or have difficulty engaging a distal pin. The suspension embodiment remains susceptible to extraneous up and down motion, pivoting, rotation and shift during ambulation. It would be greatly advantageous to supplement the suspension Harmony System to include a more stable lanyard-type fixation feature to eliminate extraneous movement. Unfortunately, this is difficult with the suspension Harmony System because the suction liner is suspended over an evacuation nozzle at the bottom of the socket that evacuates moisture (sweat) outside of the socket. This leaves little room for supplemental attachment features.
U.S. Pat. No. 6,793,682 to Mantelmacher discloses a “Sure-fit Prosthetic Attachment System” (known commercially as the KISS® System) for a transfemoral and/or transtibial prosthesis, comprising a liner for enveloping an amputee limb. The liner has a buckle suspended toward the upper end, and a corresponding strap fixedly attached on the bottom end of the liner. The anchoring system also includes a containment socket for seating the liner. The containment socket has a pair of slots there through at positions corresponding to the buckle and strap of the liner, respectively. To apply the anchoring system, the patient first applies the liner to his/her limb. The liner is then inserted into the socket with the fastening strap and buckle protruding out through the respective slots. The fastening strap is then threaded up through the buckle (running upward along the side of the socket) and are inserted there through. The patient pulls down on the strap and it works by pulley action to draw the liner down into the socket until the liner is securely seated in the socket. When fully seated, the fastening strap is secured to itself by Velcro. The foregoing forms a suspension which holds the prosthesis on. Moreover, the fastening straps through slots absolutely prevent lateral shift as well as rotation. On the other hand, the patient need only readjust the Velcro closure to adjust the position of the limb within the socket. Thus, if the limb changes position because of volume change and the distal migration of the limb into the socket, the prosthesis can easily be adjusted to compensate. Despite the advantages, the '682 patent could not heretofore be used with a locking suction liner (liner pin mating with socket) as with the Harmony System, and the '682 patent provides no drainage solution in and of itself. Integrating a drainage system into a prosthetic attachment is no easy matter without compromising comfort or stability. Just the slightest discontinuity or protruberance inside the liner can be unbearable to a patient over time.
It would be greatly advantageous to incorporate a moisture evacuation feature into the KISS® attachment system, and further to combine the KISS® dual-lanyard-type attachment and its advantages (stability, comfort, ease of application and adjustment, etc.) with the added stability of a vacuum-assisted locking suction liner as in the Harmony System to provide unmatched comfort and stability against extraneous up and down motion, pivoting, rotation and shift during ambulation.